U.S. patent application number 11/090203 was filed with the patent office on 2006-06-15 for color wheel, and color wheel assembly incorporating same.
This patent application is currently assigned to MINEBEA CO., LTD.. Invention is credited to Shigeyuki Adachi, Toshiaki Asakawa, Shinichi Niwa, Kuniyuki Takao.
Application Number | 20060126198 11/090203 |
Document ID | / |
Family ID | 36583484 |
Filed Date | 2006-06-15 |
United States Patent
Application |
20060126198 |
Kind Code |
A1 |
Niwa; Shinichi ; et
al. |
June 15, 2006 |
Color wheel, and color wheel assembly incorporating same
Abstract
There is provided a color wheel including a plurality of color
filters arranged so as to form a disk, and a retainer member
disposed at a center of the disk and formed into a C-ring defining
an open mouth portion through which an area of one color filter is
exposed. Also, there is provided a color wheel assembly which
incorporates the color wheel described above, and which further
includes a motor to rotate the color wheel, and a rotational
position detector to optically detect a rotational position of the
color wheel. Detection light emitted from the detector is set to
fall incident on the C-ringed retainer member while the color wheel
is rotated thus intermittently impinging on the open mouth portion,
namely on the one color filter, which causes the detection light
reflected thereby to come out with two different intensities that
are sensed by the detector.
Inventors: |
Niwa; Shinichi; (Iwata-gun,
JP) ; Asakawa; Toshiaki; (Iwata-gun, JP) ;
Adachi; Shigeyuki; (Iwata-gun, JP) ; Takao;
Kuniyuki; (Iwata-gun, JP) |
Correspondence
Address: |
OLIFF & BERRIDGE, PLC
P.O. BOX 19928
ALEXANDRIA
VA
22320
US
|
Assignee: |
MINEBEA CO., LTD.
Kitasaku-gun
JP
|
Family ID: |
36583484 |
Appl. No.: |
11/090203 |
Filed: |
March 28, 2005 |
Current U.S.
Class: |
359/892 ;
359/885 |
Current CPC
Class: |
H04N 9/3114 20130101;
G03B 33/00 20130101; G02B 26/008 20130101; G02B 7/006 20130101;
G02B 26/023 20130101 |
Class at
Publication: |
359/892 ;
359/885 |
International
Class: |
G02B 7/00 20060101
G02B007/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 10, 2004 |
JP |
2004-358112 |
Claims
1. A color wheel comprising: a plurality of color filters arranged
so as to form a disk configuration; and a retainer member disposed
at a center of the disk configuration; and an open mouth portion of
the retainer member, the open mouth portion overlapping one or more
of the plurality of color filters, and permitting light from a
retainer member side to pass through the open mouth portion to one
or more of the plurality of color filters.
2. A color wheel assembly comprising: a color wheel including a
plurality of color filters arranged so as to form a disk
configuration, and a retainer member disposed at a center of the
disk configuration and formed into a C-ring defining an open mouth
portion; a motor to rotate the color wheel; and a rotational
position detector to emit detection light for optically detecting a
rotational position of the color wheel, the detection light being
set to fall incident on the retainer member so as to intermittently
impinge on the open mouth portion when the color wheel is
rotated.
3. A color wheel assembly according to claim 2, wherein the
detection light impinging on the open mouth portion of the retainer
member is focused upon the color filter.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a color wheel suitable as a
filter element for a color wheel assembly as a time-share light
dispersing device, and a color wheel assembly incorporating such a
color wheel.
[0003] 2. Description of the Related Art
[0004] Recently, a projection-type image display apparatus is
increasingly coming with a time-sharing single-panel method, in
which R (red), G (green), and B (blue) lights are sequentially shed
to fall incident on one single light valve element such as a
digital micro-mirror device capable of fast switching while the
light valve element is driven in synchronization with switching of
the incident lights (R, G and B), whereby R, G and B images are
produced in a time-series manner and projected sequentially onto a
screen, or the like. Here, color composition of the images is
accomplished by a viewer due to an afterimage effect occurring at a
sense of vision. In the time-sharing single-panel method, reduction
in both dimension and weight of the apparatus, which is a feature
of a single-panel method, can be achieved by employing a relatively
simple optical system, and therefore the time-sharing single-panel
method is favorable for realizing inexpensive fabrication of a
projection-type image display apparatus. In such an image display
apparatus, a color wheel is preferably used as a filter element of
a time-share color wheel assembly to sequentially disperse light
emitted from a white light source into R, G and B lights having
respective wavelength bands in a time-sharing manner.
[0005] FIGS. 5A and 5B are respectively top plan and side views of
a conventional and typical color wheel assembly 200 as a time-share
light dispersing device including such a color wheel. Referring to
FIG. 5B, the color wheel assembly 200 comprises a color wheel 100,
and a driving motor 106 including a motor hub 105. The color wheel
100 is a tricolor color wheel composed of a disk-like substrate 101
which is made of a light-transmitting material, for example,
optical glass, and three pie-shaped (sectorial) filters 102, 103
and 104 which are formed on a surface of the substrate 101, and
which transmit exclusively, for example, R, G and B lights,
respectively. The color wheel 100 thus structured is fixedly
attached to the motor hub 105 coaxially therewith. The color wheel
assembly 200 operates such that the color wheel 100 is spun by the
driving motor 106 so that white light S impinges sequentially on
the filters (R, G and B) 102, 103 and 104 whereby the white light S
is sequentially dispersed into R, G and B lights.
[0006] There are two types of color wheels. One is a segment-type
color wheel comprising a plurality of color filter segments
prepared separately and arranged so as to form a disk, and the
other is a monolithic-type color wheel structured such that a
plurality of color filters are formed on a single disk-like
substrate.
[0007] FIGS. 6 and 7 are respectively top plan and exploded side
sectional views of a segment-type color wheel 160 comprising a
plurality (four in FIG. 6) of color filter segments (hereinafter
referred to as segments as appropriate) 112, 114, 116 and 118 which
are separately prepared and are fixed in position by means of a
support member 120 and a clamp member 122 so as to form a disk. The
clamp member 122 also functions to fixedly couple the color wheel
160 to the motor hub 105 of the driving motor 106, and a coupling
means like the clamp member 122 with such a function is usually
used when a monolithic-type color wheel, which has color filters
formed integrally on a single substrate thus not requiring a
supporting means like the support member 120, is coupled to the
motor hub 105 of the driving motor 106.
[0008] In such a color wheel assembly, a color wheel must be
rotated in synchronization with the operation of a light valve
element in order to appropriately produce images as described
above, and therefore a detector to detect the rotational position
of the color wheel is required. For example, an optical detector
for rotational position is provided, in which detection light is
radiated onto the color wheel, and variation of reflected light due
to the rotation of the color wheel is sensed, whereby the
rotational position is detected. In such a detector, a mark member
125, for example a tape, is provided on a portion of the clamp
member 122 as shown in FIGS. 6 and 7. The mark member 125 is either
larger or smaller in reflectance than the clamp member 122, and a
detector (not shown) is disposed so as to direct its detection
light to fall incident on the clamp member 122. The detection light
is reflected so as to come out with two different intensities
alternately when the color wheel 160 is rotated, and the difference
in intensity is sensed whereby the rotational position of the color
wheel 160 is detected (refer to FIG. 2 in Japanese Patent
Application Laid-Open No. H10-48542).
[0009] In the conventional color wheel and color wheel assembly as
described above, such a mark member is formed by painting, taping,
and the like, and additional component and process are required
thus incurring a cost increase.
SUMMARY OF THE INVENTION
[0010] The present invention has been made in light of the above
problem, and it is an object of the present invention to provide a
color wheel whose rotational position can be optically detected
through a combination of a color filter and a retaining means only,
and also to provide a color wheel assembly incorporating such a
color wheel.
[0011] In order to achieve the object described above, according to
a first aspect of the present invention, a color wheel is provided
which comprises a plurality of color filters arranged so as to form
a disk configuration, and a retainer member disposed at a center of
the disk configuration. The retainer member is formed into a C-ring
defining an open mouth portion.
[0012] According to a second aspect of the present invention, a
color wheel assembly is provided which incorporates the color wheel
as described in the first aspect, and which further includes a
motor to rotate the color wheel, and a rotational position detector
emit detection light for optically detecting a rotational position
of the color wheel. The detection light is set to fall incident on
the retainer member so as to intermittently impinge on the open
mouth portion when the color wheel is rotated.
[0013] In the second aspect of the present invention, the detection
light impinging on the open mouth portion of the retainer member
may be focused upon the color filter.
[0014] The color wheel and the color wheel assembly structured as
described above work so as to produce advantages to be discussed
hereinafter.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 is a plan view of a color wheel according to a first
embodiment of the present invention;
[0016] FIG. 2 is an explanatory side view of a relevant portion of
a color wheel assembly incorporating the color wheel of FIG. 1
(cross-sectioned along line A-B);
[0017] FIG. 3A is a plan view of a color wheel according to a
second embodiment of the present invention, and FIG. 3B is a
cross-sectional view of FIG. 3A taken along line A-B;
[0018] FIG. 4 is an explanatory side view of a relevant portion of
a color wheel assembly incorporating the color wheel of FIGS. 3A
and 3B;
[0019] FIG. 5A is a plan view of a typical color wheel assembly
incorporating a conventional color wheel, and FIG. 5B is a side
view of FIG. 5A;
[0020] FIG. 6 is a plan view of a conventional segment-type color
wheel; and
[0021] FIG. 7 is an exploded cross-sectional view of FIG. 6.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0022] The present invention will hereinafter be described with
reference to the accompanying drawings.
[0023] Referring to FIG. 1, a color wheel 10 according to a first
embodiment of the present invention is a segment-type color wheel
which comprises a plurality of sectorial color filter segments 12,
14 and 16 (hereinafter referred to simply as segments as
appropriate) arranged so as to form a disk, and a retainer member
18 disposed at the center of the disk and having a plurality (three
in the figure) of balancing holes 17. The segments 12, 14 and 16
have color filters 12A, 14A and 16A, respectively, formed thereon
and adapted to transmit respective lights having wavelength bands
different from one another. In the present embodiment, the color
filters 12A, 14A and 16A are constituted by dichroic filters each
formed of a dielectric multilayer film. Also, in the present
embodiment, the retainer member 18 is formed into a C-ring made of,
for example, a metal material such as aluminum, or a resin
material, and is disposed on the color wheel 10 such that the open
mouth of the C-ring is located at the segment 16. This arrangement
of the retainer member 18 results in forming an annular region 19
consisting of an upper surface 18a of the retainer member 18 and an
area D of the color filter 16A exposed through the open mouth of
the C-ring-shaped retainer member 18. The retainer member 18 is
fixed to the color wheel 10 by adhesive in the figure, but may
alternatively be fixed mechanically such that protrusions to be
formed on the retainer member 18 are engaged into holes to be
formed at the segments 12, 14 and 16 with or without adhesive
applied.
[0024] Referring now to FIG. 2, a color wheel assembly 20
incorporates the above-described color wheel 10 shown in FIG. 1
(sectioned along line A-B for the convenience of explanation), and
further comprises a motor 22 including a hub 24 and adapted to
rotate the color wheel 10, and a rotational position detector 26 to
detect the rotational position of the color wheel 10. The color
wheel 10 is fixed to the hub 24 of the motor 22 by adhesive means,
or mechanical means such as press-fitting, screwing, or combination
of the both. In FIG. 2, the color wheel 10 and the hub 24 are
attached directly to each other, but may alternatively be attached
via a support member which is optionally provided on a side surface
of the color wheel 10 opposite to a side surface having the
retainer member 18.
[0025] The rotational position detector 26 is a device to optically
detect the rotational position of the color wheel 10, specifically
such that detection light 28 is emitted so as to fall incident on
the color wheel 10 rotating, is reflected back and received by the
rotational position detector 26 which then senses variation in the
intensity of the reflected detection light 28 appearing during the
rotation of the color wheel 10, whereby the rotational position of
the color wheel 10 is detected. In the present embodiment, the
rotational position detector 26 is set so as to emit the detection
light 28 on the side surface of the color wheel 10 having the
retainer member 18, more specifically on the annular region 19
(refer to FIG. 1), thus the detection light 28 is adapted to
impinge on the retainer member 18 and intermittently on the area D
during the rotation of the color wheel 10. In this connection, the
optical system of the rotational position detector 26 includes a
light condensing means (not shown in the figure), for example, an
optical lens so that the detection light 28 incident on the area D
is focused upon the color filter 16A as schematically illustrated
in FIG. 2.
[0026] The color wheel 10 and the color wheel assembly 20
structured as described above function as follows.
[0027] Supposing that the detection light 28 is R light, and that
the color filter 16A is adapted to transmit R light, then the
detection light 28, which is set to fall incident on the annular
region 19 composed of the upper surface 18a of the retainer member
18 and the area D of the filter 16A as described above, is
reflected on the upper surface 18a of the retainer member 18 at a
certain reflectance defined by the material of the retainer member
18, and passes completely through the area D of the color filter
16A thus resulting in defining a reflectance of substantially 0%.
Since such an extremely low reflectance cannot be achieved
generally by a single material such as metal and resin of which the
retainer member 18 is made, the detection light 28 reflected at the
annular region 19 comes up with two different intensities
alternately during the rotation of the color wheel 10, and the
difference in intensity is sensed by the rotational position
detector 26.
[0028] Supposing now that the detection light 28 is R light, and
that the color filter 16A is adapted to transmit light (for
example, G light or B light) other than R light, then the detection
light 28 is reflected on the upper surface 18a of the retainer
member 18 at a certain reflectance defined as described above, and
is fully reflected on the area D of the color filter 16A thus
resulting in defining a reflectance of substantially 100%. Since
such an extremely high reflectance cannot be achieved generally by
a single material such as metal and resin of which the retainer
member 18 is made, the detection light 28 reflected at the annular
region 19 comes up with two different intensities alternately
during the rotation of the color wheel 10, and the difference in
intensity is sensed by the rotational position detector 26.
[0029] Thus, in the color wheel 10 according to the present
embodiment, the area D, which is equivalent to the mark member 125
in the conventional color wheel 160 (refer to FIGS. 6 and 7) and
works for optically detecting the rotational position of the color
wheel 10, is formed readily at the annular region 19, without using
any additional components and processes, when the retainer member
18 is attached to the segments 12, 14 and 16. And, in the color
wheel assembly 20 incorporating the color wheel 10, the area D is
optically sensed, and the rotational position of the color wheel 10
is surely detected.
[0030] A dichroic filter formed of a dielectric multilayer film has
a very high wavelength tunability about spectroscopic properties as
described above, and therefore is suitable for use as a color
filter in the present invention, but the present invention is not
limited thereto and may alternatively use any color filter defining
a reflectance that makes such a difference from the reflectance of
the material for the retainer member 18 as to be duly sensed by the
rotational position detector 28. Also, in the above discussion of
the present embodiment, the detection light 28 is R light and the
color filters 12A, 14A and 16A are light transmission-type, but the
present invention is not limited to such a arrangement, and the
detection light 28 may have a wavelength different from R light,
and the color filters 12A, 14A and 16A may be light
reflection-type, wherein an appropriate combination of the
wavelength and the color filter type is selected depending on the
specifications of the color filers 12A, 14A and 16A, the retainer
member 18, and the rotational position detector 28.
[0031] Further, since there exists a difference in level
corresponding to the thickness of the retainer member 18 between
the upper surface 18a of the retainer member 18 and the color
filter 16A, and since the detection light 28 incident on the area D
is focused upon the color filter 16A, the light detection light 28
comes up with two different reflection conditions, such as a beam
diameter, a light intensity per area, and the like, which,
according to the distance from the light emitting system of the
rotational position detector 26, are generated respectively at
reflection on the upper surface 18a of the retainer member 18 and
at reflection on the color filter 16A. Consequently, even if there
is not a sensible difference in reflectance between the area D and
the upper surface 18a of the retainer member 18, the rotational
position detector 26 can sense the difference in the reflection
conditions thus enabling detection of the rotational position of
the color wheel 10. The rotational position of the color wheel 10
can be better detected by sensing the differences in both the
reflectance and the reflection conditions. In this connection, the
level difference between the upper surface 18a of the retainer
member 18 and the color filter 16A preferably should be large in
order to increase the dynamic range of detection, and therefore the
color filter 16A may be formed on a side surface of the color wheel
10 opposite to a side surface having the retainer member 18.
[0032] A second embodiment of the present invention will
hereinafter be described with reference to FIGS. 3A, 3B and 4. In
explaining the second embodiment, any component parts identical
with those in the first embodiment are denoted by the same
reference numerals, and an explanation thereof will be omitted
below.
[0033] Referring first to FIGS. 3A and 3B, a color wheel 30
according to the second embodiment comprises a retainer member 38
shaped substantially into a two-staged C ring which is composed of
a large annular portion 38b including an open mouth, and a small
annular portion 38c integrally connected to the large annular
portion 3b coaxially and including an open mouth formed continuous
with the open mouth of the large annular portion 38b, and which
defines a center hole 39. Color filter segments 12, 14 and 16 are
fixed to the retainer member 38 such that the segments 12, 14 and
16 are fitted to the outer circumference of the small annular
portion 38c so as to form a disk and adhesively fixed to the large
annular portion 38b.
[0034] Referring then to FIG. 4, a color wheel assembly 40
incorporates the above-described color wheel 30 shown in FIGS. 3A
and 3B, and further comprises a motor 42 including a hub 44, and a
rotational position detector 26. As known from FIG. 4, the color
wheel 30 according to the present embodiment is suitable especially
when a protrusion 46 such as a rotary shaft is provided on the hub
44. Specifically, in the color wheel assembly 40, the color wheel
30 is fixedly attached to the motor 42 adhesively or mechanically
(press-fitting, screwing, or the like) in the same way as in the
color wheel assembly 20 according to the first embodiment, where
the center hole 39 of the retainer member 38 functions as an axis
hole to engagingly receive the protrusion 46. In the present
embodiment, since the retainer member 38 is formed into a C-ring
with an open mouth, the protrusion 46 is easily press-fitted into
the center hole 39 and then also stays securely engaged therewith
thus surely preventing the color wheel 30 from getting scattered
off.
[0035] In the above embodiments, the color wheel is described as
segment type, but the present invention may alternatively be
applied to a monolithic type color wheel provided with a coupling
member for attachment to a motor, in such a manner that the
coupling member is formed into a C-ring with an open mouth like the
retainer member of the present invention. This gives the same
advantages as described above.
[0036] While the present invention has been illustrated and
explained with respect to specific embodiments thereof, it is to be
understood that the present invention is by no means limited
thereto but encompasses all changes and modifications that will
become possible within the scope of the appended claims.
* * * * *